1. Field of the Invention
This invention relates generally to combustion turbines and more particularly to combustion turbines having vane segment support and alignment mechanisms.
2. Description of the Prior Art
Conventional combustion turbines comprise a compressor section, a combustion section, and a turbine section. Additionally, an annular flow path for directing a working fluid through the compressor section, combustion section, and turbine section is provided.
The compressor section and turbine section are provided with alternating rows or stages of rotating blades and stationary vane segments. The blades in the compressor section rotate to compress air which is then directed by the stationary vane segments to add momentum to the working fluid. Combustible fuel is added to the compressed working fluid in the combustion section and then heated rapidly. The heating of this mixture produces a hot, high velocity gas which is exhausted through a nozzle and directed by turbine vane segments to impinge turbine blades within the turbine section. The turbine blades then rotate a shaft that is coupled to the compressor section to drive the compressor and compress more working fluid. The combustion turbine is also used to power an external load.
Generally, the net output of a conventional combustion turbine is the difference between the total power it produces and the power absorbed by the compressor section. Approximately two thirds of combustion turbine power is used to drive the compressor section. Thus, the overall performance of a combustion turbine is very sensitive to the efficiency of its compressor section. To ensure that a highly efficient high pressure ratio is maintained, a plurality of rotating blades are axially disposed along the shaft and interspersed with a plurality of inner shrouded stationary vane segments. The vane segments provide a diaphragm assembly having stepped labyrinth interstage seals.
Typically, vane segments are closely aligned radially between the inner and outer cylinders of a turbine to minimize the aerodynamic drag on vane segments. These aerodynamic forces act normally and tangentially upon the surfaces of the vane segments and generate torques and moments that are desirably transferred to the casing of the combustion turbine rather than through the vane segments. When these torques and moments, however, act upon the vane segments, the vane segments may be misaligned, thereby reducing the compressor efficiency.
It would therefore be desirable to provide a combustion turbine with improved efficiency.